I use StumbleUpon now and then. Every now and then I turn up a site worth revisiting; reasonably frequently, I find something worth poking about in for a few minutes or something that presents a clear one-shot use like a paper or lesson plan topic. It’s a good way to scan through many sites quickly…which means that a site gets a very small amount of time in which to convince me to give it more time.
I also have my screen set up the way I like it. Firefox occupies a rough square a little smaller than the screen’s height on the right, and anything else I happen to be working on or monitoring appears to the left. Do. NOT. Mess. With. This.
I will tolerate a site that messes with this only if I absolutely have to use that site. For example, a common teaching job site in my state tries to open job listings in a new custom-sized window, and because of my Tab Mix Plus settings, the default behavior for a site trying to open a new window is to put it in a new tab. I took up right-clicking to force it into a new window while I was job searching, when I remembered. When I didn’t…I tolerated it because I had to, because many districts including some with a drivetime worth considering from here use only that site and many others use it extensively.
When I am Stumbling Upon your web site, I have no such commitment to it. My initial attention span when I’m Stumbling is about three seconds because I know that unless your site interests me in that amount of time, I can find something just as good or better in a click or two without even trying. Therefore, if it forces Firefox to reize itself, I will Stumble away before I even see what your site is about. (Note: This also applies to splash pages, because I will not click here to enter your site when I can click without having to move my mouse and have similar or better odds of getting to something interesting. Ditto for anything featuring the word “loading.”)